Why does car heat up when idling and cool down moving?

When a vehicle is idling, or standing still with the engine running, the airflow over the radiator is significantly reduced. This inadequate air circulation makes it difficult for the radiator to dissipate the heat generated by the engine effectively, leading to an increase in engine temperature.

Here's a more detailed explanation of the heat-up and cool-down processes:

1. Heat-up when idling:

- While idling, the engine generates heat from the combustion process, but there is minimal air passing through the radiator.

- The reduced airflow allows the heat to accumulate in the engine compartment and around the engine itself.

- Without sufficient cooling, the engine temperature starts to rise.

2. Cool-down while moving:

- When the vehicle starts moving, air flows through the vehicle's front end and passes over the radiator more effectively.

- This increased air circulation helps to dissipate the accumulated heat from the engine and its components.

- The radiator functions optimally to transfer the heat from the engine's coolant to the air, keeping the engine at a steady operating temperature.

In summary, the difference in airflow between idling and moving is the primary factor affecting engine temperature. Idling restricts airflow and leads to heat build-up, while driving allows for sufficient airflow and effective heat dissipation, resulting in a cooler engine.